The present invention relates to an organizer for a splice between optical fibre cables that can be used with simple dimensionally-recoverable sleeves to form a splice case.
Whilst dimensionally-recoverable, generally heat-shrinkable sleeves, have become widely used for sealing splices between copper conductor cables, they have not so far become accepted for optical fibre closures. One problem is that an optical fibre splice must be provided with an organizer (a term well understood in the art) for storing in an accessible fashion the individual fibre splices and for storing loops of fibre in order that the splice may be made a short distance, a few metres generally, away from the cables to be spliced. The spare lengths of fibre either side of the fibre splice must therefore be accommodated in the splice case. The presence of the organizer means that the splice case has a large diameter compared with that of the ingoing and outgoing cables. If a simple, unshaped, shrinkable sleeve is to be used it must have a correspondingly high shrinkage ratio: before recovery it must be large enough to surround the organizer, and after recovery it must be small enough at it ends to engage the ingoing and outgoing cables.
Optical fibre splice cases generally, therefore, comprise rigid housing, often of metal and generally rectangular shape, having holes in their sides through which the cables pass. The holes may bear tubular projections through which the cables pass. A small heat-shrink sleeve may be provided over each projection and the cable to seal the cable. Such a closure is disclosed in EP 0043570 (Siemens).
An alternative prior art design is shown in U.S. Pat. No. 4,428,645 (GK Technologies). Here two disc-shaped end plates are provided and the space between them closed by two half-shells which bear on the end plates. The end plates may be split, and in any case the ingoing and outgoing cables pass through holes in them. In both the Simens and GK Technologies designs the housing accommodates an organizer comprising a series of plates each of which may store one or more fibre splices and associated loops of fibre.
These types of prior art solutions are generally satisfactory but suffer from some disadvantages. For example they are not easily made wrap-around (a term well known in the art and, in contrast with tubular, meaning installable on a length of cable without requiring access to a free cable end) without the risk of leak paths. They tend not to be adaptable to different numbers or sizes of spliced cables. Also the quality and reliability of seal may not be high, and entirely different components and techniques from those familiar in connection with copper are required. We have now devised a simple organizer that allows a splice case to be made using standard dimensionally recoverable sleeves.